An intensive effort was directed toward studying the epidemiologic, virologic, immunologic and therapeutic aspects of the acquired immunodeficiency syndrome. An ongoing study of 983 health care providers has continued to demonstrate the low risk of HIV-1 transmission from patient to hospital worker. The polymerase chain reaction was used to identify the presence of HIV-1 genome in 3 out of 20 individuals with negative ELISA tests and indeterminate antibody profiles on Western blot. HIV-1 infection of highly purified peripheral blood CD4+ T cells has been shown to result in the outgrowth of a population of gamma-delta T cells that are defective in IL-2 production. A subset of patients with HIV-1 infection were shown to have increased numbers of gamma-delta cells in the peripheral blood. Immunization of healthy human volunteers to the gp160 envelope precursor protein of HIV-1 has elicited antibody and lymphocyte blast transformation responses to both recombinant and natural product HIV-1 proteins. A series of clinical trials were carried examining the effects of alpha interferon and AZT either alone or in combination in patients with early stages of HIV-1 infection. Attempts at immunologic reconstitution employed the immunomodulators IL-2 muramyl tripeptide and examined the role of bone marrow transplantation and syngeneic lymphocyte transfers in combination with anti-retroviral therapy. A phase I trial of a candidate AIDS vaccine, gp160 was initiated.